The present invention relates to vehicle seat systems and, more particularly, to locking mechanisms for adjustable vehicle seats.
Many aircraft and other vehicle seating applications have a requirement that the seat be able to translate in one or more directions. Once translated, the seat must be securely locked in its new location and once locked, the seat must be able to withstand various use/abuse loads, in-flight gust loads, and crash loads. Conventional seat track locking mechanisms typically employ a track member that contains a plurality of slots or holes spaced along the length of the track. The other track member has a pin or shaft that is selectively engaged with one of the holes or slots to lock the track members together. When the pin is disengaged from the hole, the tracks can move relative to one another. Once the seat is in the desired position, the pin is re-engaged in a corresponding slot or hole.
A disadvantage of this type of locking assembly is that there are only a finite number of adjustment positions, since each slot or hole defines one seat position. In order for the locking mechanism to be sufficiently robust to meet the load requirements, the pins and holes of the locking mechanism must be made sufficiently robust (i.e., large) and therefore the pitch between available locked positions is relatively coarse. Additionally, with the conventional pin and hole locking mechanisms, sufficient clearance between the pin and hole must be allowed to facilitate easy engagement of the pin with the hole. This, however, can lead to undesirably noisy and uncomfortable backlash when the seat is in the locked position.
Another type of seat locking mechanism employs a unidirectional friction lock consisting of a rod and a collar that slides over the rod. The collar is biased along one edge by a spring that causes the collar to wedge against the rod. This type of mechanism enables infinite adjustment, but because the collar can only hold in a single direction, two complete mechanisms are required to lock the seat in position. Moreover, because this type of mechanism relies on friction to hold the seat in position, it will slip if a heavy load is applied. Accordingly, seats equipped with this type of mechanism must be moved to a special position and locked in place if heavy loads are anticipated, for example, during aircraft takeoff and landing. What is needed is a seat locking mechanism that is capable of holding in two directions with a single mechanism that is sufficiently robust to meet the foregoing load requirements yet is capable of fine adjustments with little or no backlash in the locked position.